Apparatus for Automated Positioning of Eddy Current Test Probe

ABSTRACT

An apparatus for automated inspection and repair of a tube sheet. The apparatus has a rotating gripper pod, comprising at least one tube gripper, a sliding body portion containing the gripper pod; a housing portion comprising at least one tube gripper and a tool head coupling. The tool head coupling swapably attaches to a eddy current test probe and at least one kind of tube repair tool. Novel, auto-locking tube grippers are also disclosed. A serial bus connects electronic modules within the apparatus and also connects the apparatus to an external controller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and is a divisional of pendingU.S. patent application Ser. No. 12/687,261, filed on Jan. 14, 2010,which claims priority to and the benefit of U.S. Provisional ApplicationNo. 61/145,629, filed Jan. 19, 2009, each of which is incorporated inits entirety herein by reference.

BACKGROUND OF THE INVENTION

Regular inspection and testing of steam generator tube sheets iscritical to the operation of a steam generator plant. Tube sheets arearrays of parallel tubes that can be accessed at at least one endwherein the tube ends are arranged in an single plane. Testing of eachtube is delicate and time consuming. In the past, this has been done bymanually placing testing probes in the tubes. Described herein is animproved automated apparatus for positioning test and repair equipmentin a tube sheet for steam generators.

Desirable attributes of such an automated apparatus include: singleperson fast installation; integrated grab features for handling;protection bumpers; independent of tube sheet and steam generatorfeatures; simplified cable systems and single point cable connection;simplified calibration; ease of decontamination; complete integrationwith data acquisition systems; fast, accurate performance; and supportfor repair tooling.

FIELD OF INVENTION

The present invention relates to automatic inspection and repair systemsand more particularly to a robotic apparatus for positioning an eddycurrent test probe in an array of steam generator tubes.

BRIEF SUMMARY OF THE INVENTION

A robotic tool positioner especially adapted for positioning tooling andtesting equipment in a tube array, such as in a steam generator. Thetool positioner has several novel features, described herein.

In an embodiment, the tool positioner is adapted to move across the faceof a tube sheet of open tubes. The positioner includes: a sliding bodyportion containing a rotating gripper pod with the rotating gripper podhaving at least one tube gripper; left and right outer housing portionshaving at least one tube gripper each; and a tool head coupler tosupport various attachments, including an eddy current test probe,repair and maintenance tools. The sliding body portion moves laterallyacross the tube sheet with respect to the housing portion. The rotatinggripper pod allows the positioner to rotate in an axis perpendicular tothe plane of the tube sheet.

The tool head coupler provides for the attachment of test probes andrepair and maintenance tools to the sliding body portion. The robot alsoincludes machine vision and machine vision lighting.

In an embodiment, the tube grippers have a pneumatic actuator, at leastone gripper shoes and integrated sensors adapted to detect deploymentand retraction position. In an embodiment, the sensors are Hall effectsensors. The tube grippers are adapted so that the reactionary force ofthe tool positioner pulling away from the tube sheet forces the tubegripper shoes against the tube wall. To retract a tube gripper, thegripper head is pushed up into the tube slightly to release pressure onthe gripper shoes, which are then retracted by spring-loaded retractors.In an embodiment, the robot electronics, including an on-boardmicroprocessor, are interconnected by a simplified serial network thatminimizes interconnection wires between electronic modules within therobot and allows for installation of new modules and interchangeabilityand updates to existing modules without costly wiring harness changes.The robot is controlled by an external controller that communicates withthe robot over the simplified serial network. In an embodiment, thesimplified serial network is the industry standard Controller AreaNetwork or “CAN” bus.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

FIG. 1 is an isometric drawing of an exemplary design of an automatedpositioner;

FIG. 2 is an isometric view of a tube gripper head;

FIG. 3 is a cross-sectional drawing of an exemplary tube gripperinserted in a tube; and

FIG. 4 is an exploded view of an exemplary tube gripper.

DETAILED DESCRIPTION OF THE INVENTION

An inspection and repair robot is disclosed. The design provides a veryefficient footprint for moving and repositioning eddy current testprobes within a steam generator. The unique motion and small sizeprovide high flexibility in reaching all tubes within the tube sheetwithout complex repositioning motions. This provides quick and efficientmotion in positioning the robot to a target zone or specific tube. Allof this is accomplished at state of the art speed. In an exemplaryembodiment, the robot can transverse across the tube sheet at speeds ofup to 5 feet per minute for large moves and can achieve tube-to-tubespeeds during test or repair operations of up to 4 inches/second. Therobot utilizes built-in machine vision for secondary tube verificationfor all attached tooling.

Robot Body

With reference to FIG. 1, an exemplary repair and inspection robot hasan outer housing 10 comprising four housing grippers 20; a sliding bodycenter 30, comprising a rotating gripper pod 40, which has threegrippers 50. The sliding body center 30 also has a tool head interface60 comprising a tool head lock 61 with a hot shoe (not shown), machinevision lighting 63 and integrated machine vision camera 64. The toolhead lock 61 is rotatably attached to the tool head bracket 60. Therobot moves across a tube sheet (not shown) by alternately inserting andlocking grippers 20, 50 into the tubes from either the outer housing 10or the rotating gripper pod 40. It can be seen that when the threecentral grippers 50 are inserted into tubes, the outer housing 10 canrotate to any angle and translate a limited distance away from therotating gripper pod 40 via the sliding relationship between the centerbody 30 and the outer housing 10. Once the outer housing 10 hasrepositioned itself with respect to the center body 30, the tubegrippers 20 in the outer housing 10 are inserted into tubes and lockedand the tube grippers 50 in the rotating pod 40 are released andwithdrawn from the tube sheet. The sliding body 30 is then free to movewith respect to the outer housing 10 to engage new tubes. This processis repeated until the housing 10 reaches the required location on thetube sheet.

The configuration of the four outer housing grippers 20 and threerotating pod grippers 50 is designed to support a broad range of squareand tri-pitch tube sheet configuration, pitches and patterns. The bodyis designed to fit through the smallest man-way openings (not shown) inexisting equipment. The controller for the robot is also as small aspossible to maximize platform space. A small diameter control cableminimizes cable tangle.

Robot Positioning

In an exemplary embodiment, there is a host computer, which is outsidethe tube sheet environment. There is also an external controller in thetube sheet environment that communicates with the host computer and withthe robot.

The host computer and software plans the robot movements and sendscommands to the controller. It is typically remote to the radioactiveenvironment where the robot and controller work. It sends commandsthrough Ethernet to the controller which is external to the robot.

The controller communicates to the robot via a power/data cable thatcarries the CAN communication and power for the devices. The robot hasmultiple CAN devices for the specific functions. It receives andexecutes commands directly from the controller.

The controller has communication with both robot and hostcomputer/software.

Sequences for robot moves from one position to another are determined bythe host computer and transmitted to the robot external controller.

To make a move the external controller issues a command with argumentsfor the specific type of the device and an address for the device. For amotion axis, this may include commands for the motor on the axis in theform of rotation in degrees, rotation direction and rotation speed foran axis along with the address on the serial bus for the device.

The host computer software manages the logic of how to move and issuescommands to the controller which in turns formats them in to theinstructions for the devices described above.

Tube Inside Diameter Grippers

FIG. 2 shows an exemplary tube gripper head 100. The gripper head 100has three gripping shoes 110 that slide along three channels equallyspaced around the outside wall of the gripper head 100. Each channel hasan inclined surface 115 that is in contact with the gripper shoe 110.The inclined surface 115 forces the gripper shoe 110 away from thecenter of the gripper head 100 when the shoes 110 are pushed up into atube (see FIG. 3), in a direction away from the robot body 10. As such,the grippers 20, 50 are self-locking. Once the shoes 110 are forced upinto a tube, a force created by air pressure is exerted forcing thegripper bodies away from the tube sheet, thus forcing the shoes 110against the tube wall 200. When the robot is below a tube sheet, theweight of the robot pulling down on the gripper head 100 keeps the shoes110 locked against the tube wall 200, even if power is removed. When thetube sheet is not horizontal, reactionary force away from the tubeskeeps the grippers 20, 50 locked. Any force tending to pull the robotaway from the tubes will keep the grippers 20, 50 locked in place. Thegripper shoes 110 are withdrawn only by forcibly retracting the shoes110 while extending the gripper body slightly into the tube wall 200 toaid in pushing the shoes 110 back down the inclined surface 115 and awayfrom the tube wall 200.

In an embodiment, the friction between the shoe 110 face and theinclined surface 115 is reduced by a friction reduction element (notshown). It is critical to the operation of the gripper shoes 110 thatthe friction between the shoe 110 and the inclined surface 115 becontrolled so that less force is required to move the shoe 110 acrossthe inclined plane than is required to move the shoe 110 across the tubewall 200. In an embodiment, a plastic insert 111 is inserted between theshoe 110 and the inclined surface 115.

FIG. 3 is a cross section view showing a gripper head 100 inserted in atube wall 200. A gripper shoe 110 is shown pressed against the wall 200,being forced into the wall 200 by the inclined surface 115 of the slotin the gripper head 100. In an exemplary design, each gripper shoe 110is in contact with a pushrod 120. To lock the shoe 110 against the tubewall 200, the pushrod 120 is urged upward by a plate 150. When the plate150 is retracted, spring 130 loaded return pins 140 urge the pushrods120 back down, thus releasing outward pressure on the gripper shoes 110.As stated earlier, to aid in releasing the gripper shoes 110 from thetube wall 200, the entire gripper head assembly 100 is urged upward intothe tube slightly, moving the inclined surface 115 up and releasing theoutward pressure on the gripper shoes 110.

The embodiment shown is an advanced high performance gripper design thatwill not cause tube damage, yet provides high load capacity (of up to300 lbs per gripper) and automatically provides grip force to match theload applied to the robot. All of this is accomplished while remainingfail-safe during power service interruptions.

In an exemplary design, the robot tube grippers (FIGS. 2-4) have thefollowing features: self locking tube ID gripper concept where the loadof the robot helps lock and hold the lock; simultaneous deployment ofgripper 110 and toe 116 along with the locking retract step; multi-stagecustom air cylinder deployment/release mechanism, telescoping cylinders;simultaneously deploying, but individually retracting gripper shoes 110;individually replaceable gripper shoes; coatings or other frictionreduction elements to provide slip plane surface between the grippermandrel and shoe surface; hall effect, optical other type of sensor inthe gripper head senses deployment status and senses plugs in the tube;multistage pneumatic locking gripper; robot load increases lock to tubesurface; smooth gripper shoes do not impose stress points on tube wall,will not damage steam generator tubing; integrated hall sensors detectdeployment and retraction position; failsafe grip during powerinterruptions; gripper heads are designed for quick change; anddistributed 110 and on-board servo and control. Automatically andindividually adjusting each gripper for optimum positioning of gripperwithin the tube inside diameter for accommodation of variances in tubingdiameters for gripping and un-gripping operations.

In an embodiment, the position of the gripper within the tube isadaptively adjusted to account for variations in tube diameter andopening tolerances. There is an optimal depth range at which the grippershould be inserted into the tube. If the gripper is inserted too farinto the tube, it is difficult to extract, since extraction requiresextending the gripper slightly farther into the tube than the positionwhere it is anchored. Anchoring the gripper to close to the open end ofthe tube can possibly damage the tube in some situations. Thus, it isuseful to be able to locate the gripper in a limited insertion range inthe tube. One way to do this is to include a position sensor on thegripper. The position sensor can be a Hall effect sensor or opticalsensor. The gripper is inserted in the tube and locked and its positionis determined. If the gripper is not in the desired area, the gripper isreleased and re-inserted. Positioning the gripper is a function of twotiming parameters: there is a gripper insertion duration and a time atwhich the gripper shoes are forced outward to grip the tube wall. Thecombination of these two times is adjusted to place the gripper atdiffering depths within the tube. Because of variations in tube diameterand shape, the timing parameters are not universal. For this reason, anadaptive approach as described here is used to place the gripper in thedesired location by adjusting the insertion time and shoe actuation timeeach time the gripper is repositioned until the gripper is anchored atthe desired location in the tube.

Serial Network

In an exemplary embodiment, a serial network connects internalelectronic modules of the robot. The serial network also connects anyelectronics attached to the tool head, the external controller and aninstallation robot. The serial network eliminates the need for customwiring between these devices and reduces wire count, thus increasingreliability and reducing cost. The use of the serial network allows forexpansion and improvements to existing hardware since additional modulescan be added that communicate with the existing modules by simplytapping into the serial network. In an embodiment, the serial network isan electrical network and is implemented with the industry standard CANbus. In an alternate embodiment, the serial network is a fiber opticnetwork. The serial network also allows a single external controller tocontrol multiple system elements within the robot system on the samebus. An additional serial network is provided in the form of a “1-Wire”memory chip to communicate and manage information stored in systemcomponents for use in controlling system level inventory, storing ofdata and configuration of software operations. The “1-Wire” networkprovides for insuring proper system operation parameters are respectedto avoid undesirable operation.

Robot Tool Head

In an exemplary design, the robot tool head interface has the followingfeatures: quick make/break air coupling combined with electrical (powerand signal) connection and proximity/Hall effect auto-lock feature.

Control Software

Software for an exemplary design includes: kinematics, multiple robotcoordination, and collision detection/avoidance; software inspectionplanning & simulation; motion path planning algorithms to validateoperation in bowl; trajectory planning algorithms to provide optimalpath to target location; movement optimization algorithms to controlmovement around plugs and stays; and efficient inspection planningalgorithms to optimize eddy current testing inspection and delivery ofrepair tooling.

Features and Benefits

Some features and benefits of the present invention include:

Small footprint of the robot provides ultimate maneuverability froefficient repositioning in all regions of the tube sheet while occupyingless area thereby allowing the use of multiple robots per head.

Light Weight. At less than 40 lbs the robot is easily transportable andinstallable. In conjunction with the small footprint it requires lessenergy to grip into the tube sheet.

Fail-safe revolutionary gripper design ensures that the robot willremain attached to the tube sheet through loss of all power, yet remainseasily removable during emergency situations.

Fast and strong with a tube-to-tube speed of up to 4 inches/sec and upto 300 lbs load capacity per gripper. The robot is capable of performingboth high speed inspections and supporting the load demands of repairtooling.

A simplified system uses CAN-bus (Controller-area Network) controlsystem architecture. The robot provides the smallest robot cable bundlein the industry with a diameter of less than 1 inch.

Intelligent software control manages the telemetry of all robots withina steam generator to avoid robot to robot collisions as well as probecollisions with robots operating in the opposite channel head.

Seamless Interface with Zetec's MIZ®-80iD intelligent systemcapabilities for exchange information between hardware components andtooling.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1-12. (canceled)
 13. An apparatus for automated inspection and testingof a tube sheet wherein the tube sheet has a plurality of tube openingsarranged on a tube sheet plane, the apparatus comprising: a coreassembly comprising: a rotating module with three tube grippers; a toolhead coupling hingedly mounted to said core assembly; and outer housingactuators; and left and right outer housings; each outer housingcomprising one or more tube grippers; wherein said core assembly isarranged between said left and right outer housing portions, and whereinsaid core assembly, including said rotating module, and said left andright outer housing portions have top surfaces aligned on a common planewhich, when the apparatus is in use, is parallel to said tube sheetplane, and wherein said tube grippers emerge from said rotating moduleand left and right outer housings, respectively, perpendicular to saidcommon plane and wherein said core assembly actuators move said left andright outer housings with respect to said core assembly such that saidtop surfaces remain in said common plane.
 14. The apparatus of claim 13,wherein said tool head coupling supports alternately an eddy currenttest probe and a tube repair device.
 15. The apparatus of claim 13,wherein each of said tube grippers comprises an actuator; and grippershoes; wherein said gripper shoes have a tube contacting surface and aninner surface and said tube gripper further comprises a gripper shoemating surface, and a gripper shoe friction reducer wherein said grippershoe friction reducer reduces the friction between said gripper shoeinner surface and said gripper shoe mating surface such that less forceis required to slide said gripper show along said gripper shoe matingsurface than is required to slide said gripper shoe tube contactingsurface against said tube wall.
 16. The apparatus of claim 13, whereinwhen at least two of said rotating module tube grippers are locked intotubes and none of said outer housing tube grippers are inserted intotubes, the rotating module can be actuated to rotate the apparatus aboutan axis that is perpendicular to said tube sheet plane.
 17. Theapparatus of claim 13, wherein when at least two of said rotating moduletube grippers are locked into tubes and none of said outer housing tubegrippers are inserted into tubes, said outer housing actuators can beactuated to move said outer housings across the tube sheet parallel tosaid tube sheet plane.
 18. The apparatus of claim 13, wherein when atleast two of said outer housing tube grippers are locked into tubes andnone of said rotating module tube grippers are inserted into tubes, saidouter housing actuators can be actuated to move said core assemblyacross said tube sheet parallel to said tube sheet plane.
 19. Theapparatus of claim 13, further comprising a plurality of electronicmodules interconnected by a serial network, wherein said serial networkalso connects said apparatus to an external controller.
 20. Theapparatus of claim 19, wherein said serial network also connects aninstaller device to said external controller.
 21. (canceled)